Behind Pfizer’s new Covid-19 vaccine
Scientists are playing it safe: they want to see the data, but say that there is ‘reason to be cautiously optimistic’
The announcement by Pfizer and BioNTech that they have a vaccine which, early data shows, prevents 90% of Covid-19 infections has offered the world a glimpse of an end to the coronavirus nightmare.
It’s good news for everyone, perhaps with the exception of video call technology company Zoom, whose stock tumbled 17.3% on Monday as the promise grew of a resumption of travel and face-to-face meetings.
Scientists expressed excitement, while also urging caution.
There’s good reason for this wariness: the announcement came from a Pfizer press release, and not through any peer-reviewed science journal, as is usually the case with any new medical treatment.
Andrew Preston, reader in microbial pathogenesis at the University of Bath, warns that a lot is still unknown. “The actual data from the trial is not publicly available for full scrutiny, and it is noted that the trial is not yet complete,” he says.
At the moment, this vaccine is being tested on 45,538 people, half of whom are getting a placebo, with the other half getting the actual vaccine.
Pfizer said that 94 of trial participants got Covid-19, presumably in the placebo group, though that was not specified. The trial will only end when 164 cases of Covid-19 have been confirmed.
Nor has the data yet revealed if the vaccine is effective in elderly people, who are more at risk of death from Covid-19, and whose immune systems don’t always respond as well to vaccines as young people’s.
We also don’t know how long any protection lasts. Volunteers must be monitored for at least another two months to detect possible side effects, though no safety incidents have yet been recorded.
And then there’s the fact that scientists aren’t just fighting Covid-19, they’re also battling a growing wave of conspiracy theories mixed with anti-vaccine sentiment.
Preston says tackling public concerns requires “full transparency” about the vaccines and the processes leading to their use. “Until we have full transparency – the data available for independent scrutiny – we can’t be sure how much of a success this really is,” he says.
This vaccine is also unusual in other respects.
For one thing, no vaccine using mRNA technology, as Pfizer’s does, has ever been effective enough to be licensed as a vaccine before, which makes transparency even more important.
The way that vaccines usually work is that they use inactivated parts of a virus to trick the body’s immune system into fighting it. Pfizer’s vaccine, by contrast, tricks the body into making part of the coronavirus – the famous spike – before the immune system kicks in to neutralise it.
Simon Clarke, associate professor of cellular microbiology at the University of Reading, says that if this mRNA vaccine works, it offers hope for countering other illnesses.
“In the absence of any data from Pfizer and BioNTech, we have to take these very exciting claims at face value. If this vaccine makes it to the clinic, it will be the first instance of this strategy, an mRNA vaccine, being effective, and could open up many other avenues for diseases where there currently is no vaccine,” he says.
One overwhelmingly positive response to the news came from the Coalition for Epidemic Preparedness Innovations (CEPI), a foundation set up in 2016 to fund vaccine development.
CEPI CEO Richard Hatchett says many Covid-19 vaccines in development also use the spike to provoke the body’s immune system to fight the virus. This means Pfizer’s success increases “the probability of success of other Covid-19 candidate vaccines which use a similar approach”.
There are, however, lots of caveats.
If Pfizer’s trial is ultimately successful, it could manufacture 1.3-billion doses in 2021, and participants would need two shots 21 days apart. It is thought that the vaccine would be rationed first to elderly and high-risk people and health-care workers.
A far trickier problem is that this vaccine has to be kept at -70°C, in the cold chain, and cannot thaw.
But in underdeveloped areas, where vaccines are often kept at around -5°C, new infrastructure would have to be built to house the vaccine.
This is one of the reasons local drug company Aspen is partnering with Johnson & Johnson (J&J) to manufacture 300-million doses of its vaccine, if it is successful.
When Aspen announced the deal last week, senior executive Stavros Nicolaou explained that Aspen had examined different vaccine candidates carefully and chosen a vaccine that was “quite practical”.
Unlike Pfizer’s, the J&J vaccine can stay stable at -20°C and then survive at between -2°C and -8°C for at least three months, allowing it to be “compatible with standard vaccine distribution channels”.
Nonetheless, Pfizer CEO Albert Bourla called the announcement “a great day for humanity”.
Scientists are playing it safe: they want to see the data, but say that there is “reason to be cautiously optimistic”.
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